Highly stable amplified low-potential electrocatalytic detection of NAD+ at azure-chitosan modified carbon electrodes

The incorporation of chitosan (CHIT) into an Azure-C (AZU) film, covering a glassy carbon electrode, greatly facilitates the electroreduction of NAD+ to allow a highly stable low-potential amplified cathodic detection of this enzymatic cofactor. Higher and sharper NAD+ reduction peaks are thus observed at lower potentials at the AZU/CHIT coated electrode, compared to those observed at the AZU-modified electrode. Such formation of an AZU/CHIT surface layer leads also to a highly stable NAD+ response. For example, 98% of the initial amperometric response of NAD+ at the AZU/CHIT coated electrode is retained after 20 min stirring 6 × 10−3 M NAD+ solution (compared to 69% at the AZU-modified electrode). Factors affecting the enhanced electrocatalytic response, including the composition of the AZU/CHIT layer or pH, are examined. Electrochemical parameters for the NAD+ reduction, including the α, k or E0′, are estimated by cyclic voltammetry. The improved NAD+ detection of NAD+ reflects the improved film formation imparted by the CHIT component. The new modified electrode could find a wide range of biotechnological applications, including biosensors, bioreactors and biofuel cells.